الفهرس 
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Abstract
The aim of this investigation is to study chemical, physical and mineralogical characteristics of some soils in Toshka area, South of Egypt, assess land capability and suitability for growing certain crops. The studied area involves some soils lying on the terrain of branch-2 of El-Sheikh Zayed canal (about 60,000 feddans). The studied area extends between latitudes 22°54 َ57ً to 23° 07َ 19ً North and longitudes 31° 19َ 18ً to 31° 30َ 21ً East. Eighteen soil profiles were dug to represent the two geomorphological units in the studied area as follows: br 1. The alluvial deposits unit br This unit was represented by ten soil profiles 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. br 2. The pediplain unit br This unit was represented by eight soil profiles 11, 12, 13, 14, 15, 16, 17 and 18. br The soil profiles were subdivided into horizons according to the morphological differences and the profiles were morphologically described in the field. Fifty one soil samples were collected -#102;-#114;-#111;-#109; soil profiles to evaluate soil chemical, physical and mineralogical characteristics. The obtained data could be summarized as follows: br 5.1. Chemical characteristics: br Soil reaction (pH) varied -#102;-#114;-#111;-#109; 6.95 to 8.65 in the alluvial deposits units, while it differed -#102;-#114;-#111;-#109; 6.95 to 8.70 in the pediplain unit. br Soil salinity differed -#102;-#114;-#111;-#109; none saline to strongly saline as EC values of the saturated soil paste extract ranged -#102;-#114;-#111;-#109; 2.69 to 42.94 dSm-1 in alluvial deposits unit and -#102;-#114;-#111;-#109; 2.34 to 48.54 dSm-1 in the pediplain unit. br The soluble cations followed the -#111;-#114;-#100;-#101;-#114; Na+ -gt; Ca++ -gt; Mg++ -gt; K+ in both the studied units. On the other hand, the soluble anions were dominated by Cl– followed by SO4= then HCO3–. br Values of CEC differed -#102;-#114;-#111;-#109; 7.02 to 31.24 cmolCkg-1 in the alluvial deposits unit and -#102;-#114;-#111;-#109; 12.70 to 60.38 cmolCkg-1 in the pediplain unit. The exchangeable cations were dominated by Ca++ followed by Mg++ then Na+ and K+ in the alluvial deposits unit, while in the pediplain unit the exchangeable cations followed the -#111;-#114;-#100;-#101;-#114; Ca++ -gt; Na+ -gt; Mg++ -gt; K+. br Calcium carbonate content varied -#102;-#114;-#111;-#109; 0.26 to 14.20% in the alluvial deposits unit, while in the pediplain unit it ranged -#102;-#114;-#111;-#109; 0.27 to 17.90%. br Gypsum content differed -#102;-#114;-#111;-#109; 0.30 to 8.10 % in the alluvial deposits unit and -#102;-#114;-#111;-#109; 0.61 to 11.28 % in the pediplain unit. br Organic matter content was very low and did not exceed 1 % due to the arid climate prevailing in the region and the absence of vegetation. In the alluvial deposits unit, the value of organic matter content ranged -#102;-#114;-#111;-#109; 0.04 to 0.97 %, while in the pediplain unit those values differed -#102;-#114;-#111;-#109; 0.08 to 0.96 %. br Values of available macro nutrients (N, P and K) in the surface horizons of the studied soil profiles ranged between 15.35-25.20, 2.06-7.62 and 121.00-371.80 mgkg-1 for N, P and K respectively in the alluvial deposits unit. On the other hand, values of the aforementioned nutrients in the pediplain unit ranged between 22.40-40.60, 1.51-8.68 and 168.00-356.80 mgkg-1 for N, P and K, respectively. br Values of available micronutrients (Fe, Mn, Zn and Cu) in the surface horizons of the studied soil profiles ranged between 2.20-8.00, 1.10-4.47, 0.65-1.66 and 0.25-0.66 mgkg-1 for Fe, Mn, Zn and Cu respectively in the alluvial deposits unit. On the other hand, values of the aforementioned nutrients varied between 2.89-9.10, 1.10-6.50, 0.66-1.22 and 0.27-0.83 mgkg-1 for Fe, Mn, Zn and Cu, respectively in the pediplain unit. br 5.2. Physical characteristics br Soil texture differed -#102;-#114;-#111;-#109; sand to sandy clay in the alluvial deposits unit, while soil texture varied -#102;-#114;-#111;-#109; loamy sand to clayey in the pediplain unit. br Values of moisture constants varied between 20.07-63.11% for saturation percentage, 7.89-to 29.41% for field capacity, 1.89-12.65% for wilting point and 5.99-16.75% for available water, in the alluvial deposits unit. On the other hand, values of the aforementioned constants in the pediplain unit ranged between 23.61-80.92% for saturation percentage, 9.66-38.31% for field capacity, 3.85-18.18 % for wilting point and 5.80-13.20% for available water. br Values of soil bulk density varied -#102;-#114;-#111;-#109; 1.35 to 1.87 gcm-3 in the alluvial deposits unit, while these values in the pediplain unit differed -#102;-#114;-#111;-#109; 1.15 to 1.62 gcm-3. br 5.3. Mineralogical characteristics: br 5.3.1. Heavy minerals br Heavy minerals in the alluvial deposits unit were dominated by opaque minerals (49.97%) followed by pyroxenes (10.34%), amphiboles (8.99%), epidote (6.71%), zircon (4.81%), rutile (3.34%), gluconite (2.61%), garnet (2.12%), sillimanite (1.88%), glucophane (1.53%), monazite (1.39%), kynite (1.23%), apatite (0.97%), diepsite (0.91%) andalusite (0.79%), tourmaline (0.68%), ziosite (0.67%), staurolite (0.61%) and biotite (0.43%). On the other hand, the heavy minerals in the pediplain unit was dominated by opaque minerals (51.39%) followed by pyroxenes (11.11%), amphiboles (8.44%), epidote (5.20%), rutile (3.71%), tourmaline (3.60%), zircon (2.98%), sillimanite (1.69%), ziosite (1.52%), garnet (1.38%), kynite (1.24%), glucophane (1.12%), apatite (1.11%), biotite (1.10%), gluconite (1.10), diepsite (0.97%) monazite (0.88%), andalusite (0.81%) and staurolite (0.63%). br 5.3.2. Light minerals br Quartz was the most abundant light mineral (92.46 and 93.28%) followed by orthoclase (3.04 and 3.49%), plagioclase (2.89 and 1.93%) and microcline (1.60 and 1.30%) in the alluvial deposits unit and the pediplain unit, respectively. br 5.3.3. Soil uniformity and development br The frequency distribution of uniformity ratios (Z/R, Z/T and Z/R+T) indicates that the soils under consideration show a state of stratification and heterogeneity of parent material. The soils are of multi-origin due to the clear variations in values of these ratios among the different horizons of the studied profiles. br Values of Wr1, Wr2 and Wr3 indicate the presence of relatively high content of the easily weathered minerals in soils which refers that these soils could be subjected to restricted or low degree of chemical weathering for a short time and / or a recent depositional regime. br 5.3.4. Soil origin and genesis br The frequencies of pyroxenes, amphiboles and epidote indicate that all the studied soils are shown to be affected by Nile sediments. br 5.4. Soil Taxonomy br The studied soils were classified to 10 taxonomic units (family level) according to USDA Soil Taxonomy 2006 as follows: br • Typic Calcigypsids, clayey, mixed, hyperthermic. br • Leptic Haplogypsids, clayey, mixed, hyperthermic. br • Leptic Haplogypsids, fine loamy, mixed, hyperthermic. br • Leptic Haplogypsids, coarse loamy, mixed, hyperthermic. br • Sodic Haplogypsids, clayey, mixed, hyperthermic. br • Typic Haplogypsids, clayey, mixed, hyperthermic. br • Typic Haplogypsids, fine loamy, mixed, hyperthermic. br • Sodic Haplocalcids, clayey, mixed, hyperthermic. br • Sodic Haplocalcids, fine loamy, mixed, hyperthermic. br • Typic Torriorthents, fine loamy, mixed, hyperthermic. br 5.5. Land evaluation br 5.5.1. Land capability classification br 5.5.1.1. Current land capability br A. Soils of the alluvial deposits br Soils of this unit are suitable (S) for agriculture as capability index varied -#102;-#114;-#111;-#109; 51.30 to 85.50. The studied soils in this unit could be classified into the following classes: br 1. Highly suitable (S1): br Capability index of these soils is more than 75. This class represents about 20% of the studied soils in this unit. br 2. Moderately suitable (S2): br Capability index of these soils ranges between 50 and 75. This class represents about 80% of the studied soils in this unit. Three subclasses were observed in this class reflecting kinds of limitation: br • Subclass S2-s1: br Soil texture is the limiting factor in this subclass. It occupies about 10% of the studied soils in this unit. br • Subclass S2-n: br Soil salinity is the limiting factor in this subclass. It occupies about 50% of the studied soils in the alluvial deposits unit. br • Subclass S2-s1n: br Soil salinity and soil texture are the limiting factors in this subclass. It occupies about 20% of the studied soils in this unit. br B. Soils of the pediplain br Soils in this unit are suitable (S) for agriculture as values of capability index varied -#102;-#114;-#111;-#109; 62.14 to 81.23. The soils of this unit could be classified into the two following classes: br 1. Highly suitable (S1): br Capability index of these soils is more than 75. This class represents about 37.50% of the studied soils in this unit. br 2. Moderately suitable (S2): br Capability index of these soils ranges -#102;-#114;-#111;-#109; 50-75. This class represents about 62.50% of the studied soils in this unit. Three subclasses were observed in this class reflecting kind of limitations: br • Subclass S2-s1: br Soil texture is the limiting factor in this subclass. This subclass represents only 12.5% of the studied soils in this unit. br • Subclass S2-s4: br Gypsum content is the limiting factor in this subclass. This subclass represents only 12.5% of the studied soils in this unit. br • Subclass S2-n: br Soil salinity is the limiting factor. This subclass represents about 37.5% of the studied soils in this unit. br 5.5.1.2. Potential land capability br The major improvements needed to overcome the current limitations in the studied area are leaching of salinity -#119;-#104;-#101;-#114;-#101; the EC values are more than 4 dSm-1 and reducing of alkalinity (sodicity) -#119;-#104;-#101;-#114;-#101; the ESP values are more than 15. These procedures could be achieved by application of gypsum requirements to reduce ESP values to the desirable values and/or leaching salts by fresh water to remove the excess salts. br A. Soils of the alluvial deposits unit: br By applying the aforementioned improvements, the potential capability classes of the studied soils in this unit would be: br 1. Potential class (S1): br This class represents about 70% of the studied soils in this unit. br 2. Potential class (S2): br This class represents about 30% of the studied soils in this unit. This class includes subclass S2-s1 as soil texture is the limiting factor. br B. Soils of the pediplain unit br The potential capability classes of the studied soil profiles in this unit include two classes as following: br 1. Potential class (S1): br This class represents about 75% of the studied soils in this unit. br 2. Potential class (S2): br This class represents about 25% of the studied soils in this unit. Two equal (12.5%) subclasses were found in this class: br • Subclass S2-s1 as soil texture is the limiting factor br • Subclass S2-s4 as gypsum content is the limiting factor. br 5.5.2. Land suitability classification for the selected crops br Fifteen crops were selected to assess their suitability in the studied area. The selected crops could be grouped into three categories as follows: br • Field crops: maize, wheat, barley, groundnut, sesame, alfalfa and cowpea. br • Vegetable crops: carrots, onion, tomato, cabbage and watermelons br • Fruit crops: olive, guava and mango. br 5.5.2.1. Current land suitability br A. Soils of the alluvial deposits unit br The studied soils in this unit are not suitable in their current conditions (N1) for all the selected crops except some soil profiles that appear suitable (S1, S2 and S3) for maize, wheat, barley, sesame, groundnuts, alfalfa, cowpea, carrots, cabbage, tomato and olive and permanently not suitable (N2) for carrots, onion, tomato and mango. br B. Soils of the pediplain unit br The studied soils in this unit are not suitable in their current conditions (N1) for all the selected crops except some soil profiles that appear suitable (S1, S2 and S3) for maize, wheat, barley, sesame, groundnuts, alfalfa, cowpea, cabbage, watermelons and olive and permanently not suitable (N2) for carrots, onion, tomato and mango. br 5.5.2.2. Potential land suitability br In -#111;-#114;-#100;-#101;-#114; to improve land suitability for the selected crops, some improvements are required in the studied area. The major improvements are leaching of salts to reduce soil salinity, application of gypsum to reduce both values of ESP and pH and application of organic matter to enrich soil with organic carbon and nutrients. br A. Soils of the alluvial deposits unit br By applying the former improvements, the soils of this unit would become suitable (S1, S2 and S3) for all the selected crops except soil profile No.9 that appears not suitable for carrots, onion, tomato and mango. These crops are highly sensitive for gypsum (more than 5%). br B. Soils of the pediplain deposits br By applying the former improvements, the soils of this unit would become suitable (S1, S2 and S3) for all the selected crops except soil profiles No.11, 13, 14, 15, 16, 17 and 18 that appear not suitable for carrots, onion, tomato and mango. These crops are highly sensitive for gypsum (more than 5%).